The demands on cleaner and less harmful exhaust gases from internal combustion engines of e.g. motor vehicles are becoming more and more stringent, and the regulations concerning allowable emission levels specify an increasing number of chemical compounds.
Depending on the operating conditions and the composition of the ambient air, the exhaust gases from a modern motor vehicle might in fact be cleaner that the ambient air which is suctioned into the engine for the internal combustion. The reason for this is the greatly improved technology for controlling and cleaning the emissions from the internal combustion, e.g. by means of improved combustion control, catalytic converters and hydrocarbon traps in the exhaust gas system, etc.
Another previously known way of reducing the total environmental effects on the ambient air caused by an internal combustion engine of a motor vehicle is to provide the motor vehicle with means for active cleaning of the ambient air.
Accordingly, U.S. Pat. No. 3,738,088 (Colosimo) discloses an air filtering assembly for cleaning pollution from the ambient air in the path of the vehicle by means of using the vehicle and the assembly as a mobile cleaning device. According to U.S. Pat. No. 3,738,088, the ambient air is cleaned by means of being passed through filter means for removing relatively larger size particulate material and electronic precipitator means for removing relatively smaller size particulate material from the inlet air. The air filtering assembly can be provided with a post filter of catalytic, replaceable cartridge-type for cleaning the air of non-particulate or aerosol pollution such as carbon monoxide, unburned hydrocarbons, nitrous oxides, and/or sulphur oxides, and the like. The catalytic post filter is claimed to have an offsetting effect which might eliminate the need for a catalytic filter in the exhaust system of the vehicle. According to U.S. Pat. No. 3,738,088, ducting means may be utilized to direct the cleaned air from the filtering assembly to desired uses such as the fresh air or air conditioning system of the vehicle. Furthermore, the described air filtering assembly includes means for spraying a fluid into the filtering assembly for periodic cleaning and rejuvenating.
Furthermore, WO 96/22146 and WO 97/11769 disclose a method and apparatus for cleaning ambient air by the movement of a vehicle having at least one atmosphere contacting surface, and a pollutant treating composition located on said surface. In a specific embodiment, a method of coating a motor vehicle radiator with pollutant treating catalyst is disclosed. The atmosphere contacting surfaces preferably comprise a finned outer surface and are selected from the outer surface of the radiator, the air conditioner condenser, the surfaces of the radiator fan, engine oil cooler, transmission oil cooled, power steering fluid cooler and air charge cooler, wherein the outer surface of the air conditioner condenser and radiator are the most preferred. The polluting treating compositions are said to include catalyst compositions useful for catalyzing the conversion of pollutants to non-objectionable materials, or alternatively, adsorption compositions for adsorbing pollutants which can be destroyed upon adsorption, or stored for further treatment at a later time. In the case of adsorption compositions, hydrocarbons and particulate matter can be adsorbed and subsequently treated by desorption followed by catalytic reaction or incineration. Advantages of the disclosed method and apparatus are claimed to be that no additional filter or apparatus is required, and that no additional energy source or changes in the construction of method of operation of the motor vehicle are required. According to WO 96/22146 and WO 97/11769, a number of pollutants in the ambient air can be treated, e.g. carbon monoxide, different hydrocarbons, nitrogen oxides and sulfur oxides.
However, the previously known techniques for cleaning ambient air in the vicinity of a motor vehicle usually require that a filter cartridge or the like is replaced manually when it has been saturated with pollutants, or that a special, rather complicated system for periodic cleaning is provided.
Furthermore, the existing systems for cleaning ambient air do not make use of the possible heat content in the treated pollutants for the internal combustion.